Kel dyes his hair because I don’t know why, and there’s a few instances of willing and unwilling hair dyeing in Campus Safari. I’m pretty sure it’s a whenever (or whenever someones are making trouble) thing.

I would think, considering the advances in materials technology in Cyantian society, that such advances likely extend into the fashion sphere. I should think fur and hair dying wouldn’t be uncommon, and likely there are a variety of available dyes, running from the short-term one-use wash-out types that come out the next time you shower to long-term types that might last for months if used properly, not unlike our current hair dyes.
It has already been mentioned that there exists dyes with glitter in it, most likely including an adhesive a little like hair spray and fine metallized plastic particles, akin to our Mylar.
As far as I can tell, society-wise, fur and hair dye seem to be unrelated to specific social events and purely a matter of personal fashion taste and preference. With the above-mentioned materials advances, it is reasonable to assume that such might be allowed from an early age, though likely under some form of parental supervision, and almost as likely (if the parent is wise) to include the less-permanent short-term dyes.

Just my two credits thrown in.

As for Darius, someone, for the love of the gods, get an orbital cutter up above him, because sure as there’s a sun in Cyantia’s sky, Celina’s going to hit him SO hard he’ll NEED orbital assets to bring him home!